Hat is a commonly used article for shading purpose. It generally is formed in different styles for use in different occasions. When not in use, it is difficult to store. This is a problem frequently occurred to the conventional hats.
In order to form the desired styles and shapes, the conventional hat usually is made from hard material. Once made, the form is fixed and not alterable. It is quite bulky and difficult to fold and store. It is inconvenient and troublesome to carry. To overcome the storing and carrying problems, many proposals have been disclosed in the prior art. U.S. Pat. Nos. 5,450,629 and 1,213,447 are two of the examples. No. 1,213,447 discloses a visor that has longitudinal fold lines to divide the visor into eight equal portions (referring to FIG. 1). It may be folded by bending inwards and outwards alternately to form a W-shape to reduce the size (referring to FIG. 2). However, such a folding structure creates some problems in use, carrying and storing, notably:                1. Folding the visor in W-shape expands the size after folding is completed. It cannot be stacked and positioned as desired.        2. The W-shaped visor has fold lines on two sides. After extended, it is difficult to form an arched shape and lacks aesthetic appealing.        3. The W-shaped visor after folding has opening ends and cannot be encased for storing.        
U.S. Pat. No. 5,450,629 discloses a convertible hat with a foldable visor. It has a visor divided by longitudinal fold lines into four equal portions, and also is folded in W-shape to shrink the size (referring to FIG. 3). It has an inner edge connecting to a shell to cover user's head. The shell may be used to encase the W-shaped visor. However, it also adopts the W-shape folding approach. Thus the size it can shrink is limited. And the W-shape folding also creates openings that cannot be covered or tied by the shell or strap.